Recently, post genome researches have been intensively and world widely done aiming for specific gene analysis: technologies, gene therapies and tailor made medical treatments. As for the gene analysis technology, a method of detecting DNA using a DNA microarray, for example, is used. According to this detection method, simultaneous analysis of expression, functionality, mutation and the like of a plurality of genes can be conducted simply and quickly.
In the detection method using a DNA microarray, DNA chips obtained by spot-fixing many sequences (probe nucleic acids) of DNA or oligonucleotide on a substrate made of glass, silicon or the like are used. By hybridization of a probe nucleic acid fixed on a substrate with a labeled sample RNA or DNA (target nucleic acid), a labeled nucleic acid having base sequence complimentary to that of the probe nucleic acid is selectively bound to the probe nucleic acid. After drying of the microarray, the fluorescence intensity of the labeled target nucleic acid is measured.
A fluorescence dye is widely used for labeling. High fluorescence intensity, emission even under dry conditions (solid conditions), water solubility, and the like are required for the fluorescence dye. As the fluorescence dye, for example, Cy3 and Cy5 are used (see, e.g., Science 283, 1 Jan. 1999, pp. 83-87).